Imaging shows TB’s staying power, confirms need for better strategies

Lesions left in the lungs by tuberculosis (TB) can outlast antibiotics and long withstand the body’s own immune system, a new PET/CT-based study has shown.

The National Institutes of Health, which funded the research, says investigators used the nuke-imaging combo to see what was going on in the lungs of 99 patients with pulmonary TB in South Africa before, during and after medication.

Lead author Stephanus Malherbe of Stellenbosch University in Cape Town and colleagues found that, after six months of completed treatment, the PET/CT scans of 76 of these 99 patients showed lung lesions similar to those seen in untreated pulmonary TB patients.

Moreover, a full year after treatment ended, 50 patients still showed radiological abnormalities, according to a Sept. 6 NIH press release.

Most of the lesions shrunk and became less severe. However, only 16 of those patients with such abnormalities were fully cleared of TB lesions. The remaining 34 patients still had significant residual lesions, NIH reports.

The researchers further found TB genetic material in saliva and mucus swabbed from a “substantial number of patients deemed to be cured of clinical symptoms at the end of treatment.”

The present study builds on previous research showing that PET/CT can be used to successfully predict the effectiveness of TB drug regimens.

It was also previously established that the microbe that causes TB, Mycobacterium tuberculosis, can live on in the lungs even after tissue samples test negative.

The new PET/CT and subsequent findings “show that TB bacteria may persist in the lungs even after patients have finished treatment and are free of clinical symptoms,” NIH says. “Although it is unclear how this might affect the risk of disease relapse, the study results underscore the need for new diagnostic methods and improved TB treatment strategies.”

The Malherbe et al. study is running in Nature Medicine.